This application claims the priority of Korean Patent Application No. 2004-40029, filed on Jun. 2, 2004, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a plasma processing system, and more particularly, to a plasma processing system having a plasma confining portion that is designed to vary a plasma confined area.
2. Description of the Related Art
In the fabrication of a variety of semiconductor devices, a process for depositing layers of material and a process for etching the deposited layer in a predetermined pattern are required. The etching of the deposited layer may be accomplished by a variety of techniques including a plasma etching process. In the plasma etching process, plasma is formed from an etchant gas source. As the design rule becomes more constraining, process conditions for the plasma etching process varies according to processes, different types of plasma etching systems have accordingly been proposed.
Among the different types of plasma etching systems, a plasma etching system in which a confining ring defining a plasma area is disposed above an edge of a wafer has been proposed. An example of such a plasma etching system is disclosed in U.S. Pat. No. 6,492,774 B1. However, due to the structural limitation of the confining ring, the plasma etching system can be effectively applied only to a fixed plasma area.
FIG. 1 shows an exemplary plasma etching system with a typical confining ring. FIG. 2 more specifically depicts such a typical confining ring.
Referring to FIGS. 1 and 2, wafer support portion 25 for supporting a wafer 10 is installed in a wafer processing chamber. An upper electrode 21 is disposed beneath a chamber lid 23 opposite to a surface of the wafer 10. A lower electrode (not shown) may be disposed on a bottom of the wafer supporting portion 25.
The upper electrode 21 (or the lower electrode) is provided to form plasma from a reactive gas injected into the processing chamber. Radio frequency (RF) power may be applied to the upper electrode 21 (or/and the lower electrode) to form the plasma. The RF power applied on the lower electrode makes ions of plasma to be accelerated. Meanwhile, the wafer supporting portion 25 can be formed in a variety of designs to support and fix the wafer 10. For example, the wafer supporting portion may be designed in an electrostatic chunk (ESC).
A confining portion 30 is disposed above an edge region of the wafer 10 to confine the plasma above an area of the wafer 10. That is, the confining portion 30 functions to define an area of the plasma and control the etchant gas pressure. At this point, since the confining portion 30 is fixed when being viewed in a direction of an X-axis, a plasma confining area 27 is confined in a fixed range on the X-axis.
That is, even when the confining portion is comprised of a plurality of confining rings 31, 33 and 35 spaced away from each other and aligned in a direction of a Y-axis, since each confining ring 31 (33 and 35) is limited to a fixed ring-shape structure as shown in FIG. 2, the configuration of inner area 28 of the confining ring 31 are not varied but fixed. This means that an X-axis range of the plasma confining area 27 is fixed.
As described above, when the confining portion 30 having the fixed confining rings 31, 33 and 35 is used, it is impossible to vary the X-axis range of the plasma confining area 27. Therefore, a plasma confining area in the plasma etching system using the fixed confining portion 30 has to depend on the adjustment of the pressure in the plasma confining area 27 or a change of the material. The adjustment of the pressure may be possible by moving the confining rings 31, 33 and 35 in the direction of the Y-axis or varying a gap between the confining rings 31, 33 and 35.
However, the adjustment of the pressure in the plasma confining area 27 cannot fulfill a variety of conditions required during the etching process. The conditions required may be considered in accordance with each step of the etching process. Some of the required conditions may have a relationship trading off each other. Accordingly, when the confining condition is varied by moving the confining portion 30 only in the direction of the Y-axis (a vertical direction to the wafer 10), other property may be shifted, making it difficult to fulfill all different conditions required in the etching process.
For example, in a step of the etching process in which etch rate is an important consideration, it is preferable that plasma confinement be a priority. In a step of the etching process where uniformity is an important consideration, it is preferable that the plasma confining area 27 be relatively large. However, as shown in FIGS. 1 and 2, when the confining rings 31, 33 and 35 are designed in the fixed ring structure, since it is impossible to expand or contract the ring in the direction of the X-axis, it is also impossible to increase or reduce the plasma confining area 27.
As the design rule becomes more constrained, and a variety of process conditions are required in performing the plasma etching process, there is a need for a plasma etching system that can more freely adjust the plasma. That is, since different processing conditions are required for each step of the etching process, it becomes more essential to more freely vary the plasma confining area 27 for each step of the etching process. Particularly, it is now more necessary to freely expand or contract the inner area 28 of the confining ring 30.